In the spirit of even more TIMTOWTDI, here's the solution for unpack(), which is another good trick to have in your bag :

$a = "de0400Newark";
print join( ",", unpack( "a2a4a*", $a ));
[download]

Read in the manpage about how unpack() can help you to unpack structured data. Sometimes this is faster than using a regular expression, sometimes it is slower.

I just noticed that you only want the number instead of all that data. So here's the code which will give you the number :

$a = "de0400Newark";
print( (unpack( "a2a4a*", $a ))[1] );
[download]